Wireless run-in position sensing systems methods

ABSTRACT

A method of performing real-time position sensing includes conveying a tool attached to a tubular string in a borehole. The tool includes a position sensing sub, and the position sensing sub includes sensing devices. The method further includes recording measurements taken by the sensing devices. The method further includes determining based on the measurements, a position along the borehole of a particular portion of the tubular string. Data from sensing devices having a higher priority overrides collecting data from sensing devices having a lower priority. The method further includes transmitting the position wirelessly.

BACKGROUND

In the oil and gas industry, some operations require accurate placementof tools downhole. For example, perforation guns should be carefullypositioned to control the location of perforation points relative to bedboundaries and relative to each other. In order to achieve suchplacement, a “dummy run” may be performed. A dummy run refers toperforming a round trip in and out of the borehole using a partiallycompleted tool string with the typical objective of confirming theposition of a particular portion of the tool string along the boreholefor a subsequent actual run using a complete tool string. For example, adummy run may confirm that the position of perforation guns during theactual run will be within the relatively small range of positions idealfor the perforation operation. Such a range is on the order of a fewfeet while the borehole may be thousands of feet long.

As borehole lengths increase, the time and cost required for the dummyrun also increases. Additionally, rented equipment also adds to thecost. For example, rig rentals may cost up to $1 million per day, and adummy run may require half of a day or more to complete. Consideringonly these two variables, the dummy run may cost $500,000. Othervariables may also increase the cost of the dummy run, leading toinefficient use of resources.

BRIEF DESCRIPTION OF THE DRAWINGS

Accordingly, there are disclosed herein a number of wireless run-inposition sensing systems and methods. In the following detaileddescription of the various disclosed embodiments, reference will be madeto the accompanying drawings in which:

FIG. 1 is a contextual view of an illustrative perforation environment;

FIG. 2 is an external view of an illustrative position-sensing sub;

FIG. 3 is a function-block diagram of an illustrative position-sensingsub;

FIG. 4 is a flow diagram of an illustrative method for real-timeposition sensing; and

FIG. 5 is a contextual view of an illustrative drilling environment.

It should be understood, however, that the specific embodiments given inthe drawings and detailed description thereto do not limit thedisclosure. On the contrary, they provide the foundation for one ofordinary skill to discern the alternative forms, equivalents, andmodifications that are encompassed together with one or more of thegiven embodiments in the scope of the appended claims.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components and configurations. As one ofordinary skill will appreciate, companies may refer to a component bydifferent names. This document does not intend to distinguish betweencomponents that differ in name but not function. In the followingdiscussion and in the claims, the terms “including” and “comprising” areused in an open-ended fashion, and thus should be interpreted to mean“including, but not limited to . . . ”. Also, the term “couple” or“couples” is intended to mean either an indirect or a direct electricalor physical connection. Thus, if a first device couples to a seconddevice, that connection may be through a direct electrical connection,through an indirect electrical connection via other devices andconnections, through a direct physical connection, or through anindirect physical connection via other devices and connections invarious embodiments.

DETAILED DESCRIPTION

The issues identified in the background are at least partly addressed bywireless run-in position sensing systems and methods. A position-sensingsub that wirelessly transmits position information in real time enablesaccurate positioning of an operational tool without requiring any extratrips or adjustments of the tool string. Additionally, the tool stringneed not be pulled out of the borehole for the reading of logs.Accordingly, the dummy run may be eliminated, and as a result, the costsassociated with the dummy run may be saved.

The disclosed systems and methods for implementing such position sensingare best understood in terms of the context in which they are employed.As such, FIG. 5 shows an illustrative drilling environment. A drillingplatform 2 supports a derrick 4 having a traveling block 6 for raisingand lowering a bottomhole assembly (BHA) 19. The platform 2 may also belocated offshore for subsea drilling purposes in at least oneembodiment. The BHA 19 may include one or more of a rotary steerablesystem, logging while drilling system, drill bit 14, reamer, anddownhole motor 26. A top drive 10 supports and rotates the BHA 19 as itis lowered through the wellhead 12. The drill bit 14 and reamer may alsobe driven by the downhole motor 26. As the drill bit 14 and reamerrotate, they create a borehole 17 that passes through various formations18. A pump 20 circulates drilling fluid 24 through a feed pipe 22,through the interior of the drill string to the drill bit 14. The fluidexits through orifices in the drill bit 14 and flows upward to transportdrill cuttings to the surface where the fluid is filtered andrecirculated.

A data processing system 50 may be coupled to a measurement unit on theplatform 2 by a wired connection 49 or wireless connection, and mayperiodically obtain data from the measurement unit as a function ofposition and/or time. Software (represented by information storage media52) may run on the data processing system 50 to collect the data andorganize it in a file or database. The software may respond to userinput via a keyboard 54 or other input mechanism to display data as animage or movie on a monitor 56 or other output mechanism. The softwaremay process the data to optimize oilfield operations as described below.

Wired telemetry, which uses an electrical line, wireline, or cable tocommunicate with the surface, has several disadvantages compared towireless telemetry. First, the line must be installed in or otherwiseattached to the drill string. As such, the line is prone to damage inthe harsh downhole conditions. As a result, the system is unreliable,which results in costly inspection, servicing, and replacement of theline. Second, the downhole motor should be particularly designed toaccommodate the line because the movement of the motor degrades the linewithout such accommodation. Such customization is expensive.

In various embodiments, wireless methods, such as acoustic andelectromagnetic (EM) telemetry, are used for communication with thesurface. With regard to acoustic waves, typically, an acoustic signal isgenerated near the drill bit 14 and is transmitted through the drillpipe, mud column, or the earth. Specifically, the drill string mayinclude an acoustic telemetry transceiver that transmits telemetrysignals in the form of acoustic vibrations in the tubing wall of thedrill string. An acoustic telemetry receiver may be coupled to the kellyto receive transmitted telemetry signals. One or more repeaters may beprovided along the drill string to receive and retransmit the telemetrysignals. The repeaters may include both an acoustic telemetry receiverand an acoustic telemetry transmitter.

Electromagnetic telemetry can be employed in a variety of ways. Usingone technique, electromagnetic signals are modulated according to asensor response to represent one or more parameters of interest. In oneembodiment, these signals are transmitted from a downhole EMtransceiver, through intervening earth formation, and detected as avoltage or a current using a surface transceiver that is typicallylocated at or near the surface. The one or more parameters of interestare extracted from the detected signal. Using another electromagnetictechnique, a downhole transceiver creates a current within the drillstring, and the current travels along the drill string. This current istypically created by imposing a voltage across a non-conducting sectionin the downhole assembly. The current is modulated according to thesensor response to represent the one or more parameters of interest. Avoltage between the drilling rig and a remote ground is generated by thecurrent and is measured by a surface transceiver, which is at thesurface. The voltage is usually between a wire attached to the drillingrig or casing at the surface and a wire that leads to a groundedconnection remote from the rig. Again, one or more parameters ofinterest are extracted from the measured voltage. Alternately, the oneor more parameters of interest can be extracted from a measure ofcurrent.

The borehole 17 may be thousands of feet long, and an operational toolsuch as a perforation sub must be placed accurately within a few feet inthe borehole 17. FIG. 1 illustrates a position-sensing sub that may beplaced on the drill string or a tool string that enables such placement.

FIG. 1 shows an illustrative perforation environment 100. (Though theseprinciples are described in terms of a perforation operation, they arealso applicable to those other operations requiring accurate placementof tools along the borehole, e.g. positioning of a shear sub or packer,multi-zone testing applications, and completion applications.)

A borehole 118 is cased using multiple concentric casing strings 116,each string having casing joints attached together by casing collars 104having threaded connectors. To preserve the integrity and rigidity ofthe casing string 116, the casing collars 104 are made with thickersteel walls. The casing joints have fairly standard lengths, enablingthe collars 104 to serve as convenient position markers or “milestones”.The thicker steel walls enable the collars to be detected with “casingcollar locators”, which may employ induction sensors or permeabilitysensors. Selected casing collars or positions along the drillstring maybe additionally tagged with radioactive markers to make them detectableby a gamma ray logging tool.

A tubular string, such as a tool string 102, includes operational toolssuch as a perforation sub 110 and a position-sensing sub 114.Perforation is a process used to establish a flow path of hydrocarbonsfrom the formation to the borehole by creating one or more holes in thecasing and any cement sheath surrounding the casing. The perforation sub110 includes perforation guns 112 to create such holes. The perforationguns 112 may be a known distance from other portions of the tool string102, such as the position sensing sub 114, and this distance may be usedin order to accurately position the perforation guns 112.

The position-sensing sub 114 includes sensing devices such as anaccelerometer, gyroscope, casing collar locator, radiation sensor,roller counter 106, and the like. In various embodiments, differentcombinations of any or all the sensing devices are included on theposition-sensing sub 104. The accelerometer detects inertial movementalong the borehole to measure acceleration. The gyroscope includes someform of rotation sensor for measuring the tool's orientation, e.g., aspinning wheel mounted on a gimbal assembly. The casing collar locatorincludes two magnetic poles positioned on either side of a central coil.Magnetic lines of flux in the casing collar locator are temporarilydistorted when the position-sensing sub 114 passes the thicker walls ofa casing collar. This distortion changes the magnetic field around theconducting coil, and the change is detected. A radiation sensor such asa gamma ray log includes a scintillation crystal and a photomultipliertube to measure gamma-ray radiation emitted by the tag or marker. Theroller counter 106 detects the distance traveled by the position-sensingsub 116 along the borehole 114, and is described in detail with respectto FIG. 2.

FIG. 2 illustrates an external view of the position-sensing sub 200,which includes a roller counter 201. The roller counter 201 is a sensingdevice that measures distance traveled along the borehole, and theroller counter includes extension arms 204 resiliently coupled to thebody of the position-sensing sub 200 by fasteners such as hinges 206 andbiased outwardly to press against the inner walls of the casing string.The hinges 206 enable the extension arms 204 to deploy by extending awayfrom the body of the position-sensing sub 200 such that wheels 202located at the opposite end of the extension arms 204 contact the casingstring and turn as the position-sensing sub 200 is conveyed along theborehole. In at least one embodiment, springs on the extension arms 204keep the wheels 202 in contact with the casing string. The wheels 202are coupled to the extension arms 204 by axles, and the deployment ofthe extension arms 204 may be initiated and controlled from the surfaceor downhole. As the casing string decreases in diameter, the hinges 206enable the extension arms 204 to retract such that the wheels 202maintain contact with the casing string. The extension arms 204 may alsofully retract when the tool string is pulled out of the borehole. Thisretraction may also be initiated and controlled from the surface ordownhole.

Encoders coupled to the wheels 202 count the rotations of the wheels202. One encoder may be used for each wheel 202, and an encoder mayinclude a rotational counter coupled to the axle of the correspondingwheel 202. In at least one embodiment, the encoder transmits a signal,such as an electrical pulse, for every rotation of the wheel 202, andthe pulse is detected and recorded by circuitry on the position-sensingsub 200. In other embodiments, fractional rotations or rotations greaterthan a single rotation are detected and recorded.

Multiple extension arms 204 provide centralization of theposition-sensing sub 200 within the borehole; redundancy that mitigatesfailure of a wheel 202, such as a seized bearing preventing rotation;redundancy that mitigates an electrical connection problem between thewheel, encoder, and circuitry; and redundancy that mitigates a wheel 202slipping (not rotating) along the casing string. Because of suchredundancies, outliers in the data measured by the roller counter may beeliminated during real-time processing without reducing the accuracy ofthe final data set. Such processing may be performed by the processor asdescribed with respect to FIG. 3.

FIG. 3 illustrates a block diagram of a position-sensing sub 302. Asdescribed above, the position-sensing sub 302 includes sensing devices308 such as an accelerometer, gyroscope, collar locator, radiationsensor, roller counter, and the like to measure downhole conditions. Theposition-sensing sub 302 also includes a processor 304, coupled tomemory 306, to process operations, store data, and calculate theposition of various portions of the tools string in real time using datameasured by the sensing devices 308.

In at least one embodiment, data from sensing devices 308 having ahigher priority overrides conflicting data from sensing devices 308having a lower priority during position determination, and the moreaccurate sensing device (determined a priori in at least one embodiment)is given the higher priority. For example, the casing collar locator maybe known to fail to detect some collars while the radiation sensor maybe known to detect a radioactive tag reliably. As such, the radiationsensor is given a higher priority than the collar locator because theposition information of the radiation sensor is more accurate.Accordingly, when the data measured by the casing collar locatorconflicts with the data measured by the radiation sensor, the latter isgiven priority during position determination. In this way, the sensingdevices 308 make up a hierarchy of higher and lower priority sensingdevices 308 relative to one another. In at least one embodiment, theradiation sensor has the highest priority, the casing collar locator hasthe second-highest priority, and the roller counter has thethird-highest priority. By using a combination of sensing devices 308and overriding conflicting data from lower-priority sensing devices, theposition of various portions of the tool string including theposition-sensing sub 302 and operational tools such as a perforation gunmay be accurately determined.

The position-sensing sub 302 also includes communication and networkinghardware 310 for enabling communications between the position-sensingsub 302 and the surface. The communication channel between theposition-sensing sub 302 and the surface is wireless. As such, positioninformation can be communicated to the surface in real-time and suchcommunication may occur continuously, automatically after a thresholdamount of time or inactivity has passed, in response to queries orprogrammable events (discussed below with respect to FIG. 4), or somecombination of the preceding.

FIG. 4 is a flow diagram of an illustrative method 400 of real-timeposition sensing beginning at 402 and ending at 414. At 404, a toolstring is conveyed through a borehole. The tool string includes aposition-sensing sub, and the position sensing-sub includes sensingdevices as described above. The tool string may also include operationaltools that should be positioned accurately downhole such as aperforation sub, a packer, a shear sub, and the like. The tool stringmay be assembled such that the position-sensing sub resides below apacker and above perforation guns when within the borehole.

At 406, measurements taken by the sensing devices are recorded.Specifically, the sensed data may be processed by a processor and storedin memory. Such processing may include pruning sensed data that isunreliable. For example, the accuracy of the wheels on the rollercounter may be determined by identifying the wheel that has turned themaximum number of times (or at the fastest speed) over a programmabledistance along the borehole. Such a wheel is a “representative” wheel,meaning that the sensed data provided by other wheels along the distanceis ignored for purposes of position determination. However, along asubsequent portion of the borehole, another wheel may be selected as therepresentative wheel. By repeating selection of the representative wheelover several distances along the borehole, the accuracy of the rollercounter increases even though various wheels may fail to rotate alongdifferent portions of the borehole.

At 408, a query or event trigger is obtained. A query may include awireless signal or command sent from the surface requesting positioninformation, while an event trigger may include a programmable thresholdof time passing, a programmable period of inactivity passing, aprogrammable distance traveled, detection of a collar, detection of aradioactive tag, and the like. If a query or trigger event is obtained,the current position is determined at 410. If not, the tool string isconveyed further through the borehole at 404.

At 410, a position along the borehole of a particular portion of thetool string is determined based on the recorded measurements. Forexample, the position of the position-sensing sub may be determined orthe position of a particular operational tool, such as a perforation subor perforation guns, may be determined. A radiation tag detected by theradiation sensor resides at a known location in the borehole. As such,the data sensed by the radiation sensor may be used to determinedistance using a database or lookup table. Collars reside at a knowndistance apart from each other. As such, the data sensed by the collarlocator may be used to determine distance by multiplying the amount ofcollars detected with the distance between the collars. The rollercounter may be used to determine distance by multiplying the number ofrotations of the representative wheels by the circumference of thewheels. Finally, the accelerometer and gyroscope may be used todetermine distance by using a dead-reckoning algorithm—i.e. the processof calculating a current position by using a previously determinedposition, or fix, and advancing that position based upon current speedsover elapsed time and course—with the collars or radioactive tag asfixes.

The distance determined from sensed data from the multiple sensingdevices may be compared to identify error and update an error factor inany of the sensing devices. For example, using dead reckoning, each timethe accelerometer and gyroscope sensors encounter a “fix,” the fixdistance may be compared with the estimated distance at the location ofthe fix. A fix is evidence of a known location, in this case, evidenceof a known distance along the borehole. The difference between the twovalues is the error factor, and as more fixes are encountered, the errorfactor is updated. Ultimately, when no more fixes are encountered, theerror factor may be used to adjust the distance measurement derived fromthe accelerometer and gyroscope measurements. In this way, thelower-priority devices may be recalibrated when presented withconflicting data from higher-priority devices. For example, the collarcount is recalibrated every time a radiation marker is detected, and theaccelerometer and gyroscope are recalibrated whenever a collar isdetected.

The distances determined from sensed data from the multiple sensingdevices may be combined to determine the current position of theposition-sensing sub and/or the position of an operational tool. Forexample, the casing collar locator measurements may supplement theradiation sensor measurements because casing collars are more frequentlypassed than radioactive tags. In the same way, the accelerometer andgyroscope measurements may supplement the casing collar locatormeasurements for positions between casing collars. Such supplementationmay occur if the data does not conflict. If the data does conflict, thendata from the higher-priority devices will override data from thelower-priority devices during the combining. For example, the data fromthe lower-priority devices may be ignored during the combining. Asanother example, the data from the lower-priority devices may be givenless weight during the combining. However, such overriding does notapply to all data from a lower-priority device, i.e. the lower-prioritydevice is not eliminated from providing data entirely. Rather, onlythose portions along the borehole where a higher-priority deviceprovides conflicting information will be subject to such override.

At 412, the position is reported. For example, the position informationis transmitted to the surface wirelessly in real time. After theposition information is reported, the operational tool, such as theperforation guns on the perforation sub, is activated without bringingthe tool string out of the borehole in at least one embodiment.

A method of performing real-time position sensing includes conveying atool attached to a tubular string in a borehole. The tool includes aposition sensing sub, and the position sensing sub includes sensingdevices. The method further includes recording measurements taken by thesensing devices. The method further includes determining, based on themeasurements, a position along the borehole of a particular portion ofthe tubular string. Data from sensing devices having a higher priorityoverrides conflicting data from sensing devices having a lower priority.The method further includes transmitting the position wirelessly.

The sensing device with the highest priority may include a radiationsensor that detects a radioactive tag. The sensing devices may includean accelerometer and a gyroscope. The sensing devices may include aroller counter. The roller counter may include wheels that turn as thetool is conveyed in the borehole, and recording the measurements mayinclude determining the accuracy of the wheels. Determining the accuracymay include determining the wheel that has turned the maximum number oftimes over a programmable distance along the borehole and recording thatnumber as a measurement for use in position determination. The methodmay include repeating the determining and recording over anotherprogrammable distance along the borehole. The tubular string may includeperforation guns, and determining the position may include determiningthe position of the perforation guns. The method may include activatingthe perforation guns after determining the position without bringing thetool out of the borehole. The tool may be attached to the tubular stringat a known distance from the perforation guns. Determining the positionmay include determining the position of the position sensing sub. Themethod may include assembling the tubular string such that the positionsensing sub resides below a packer and above perforation guns whenwithin the borehole. Programmable events may trigger positiondetermination and updating of an error factor used to calibrate theposition. Determining the position may include determining the positionrepeatedly over programmable distances along the borehole.

An apparatus for performing real-time positon sensing includes ahierarchy of sensing devices. The sensing devices measure conditionswithin a borehole as the apparatus is conveyed along the borehole whileattached to a tubular string. The apparatus further includes a processorcoupled to the sensing devices. The processor determines position usingdata from the sensing devices. Data from sensing devices having a higherpriority overrides conflicting data from sensing devices having a lowerpriority during position determination. The apparatus further includestelemetry equipment coupled to the processor, and the telemetryequipment wirelessly communicates the position.

The sensing devices may include a radiation sensor for detecting aradioactive tag, a roller counter, and a collar locator for detectingcollars. The radiation sensor may have the highest priority. Theprocessor may determine the position of the apparatus using the datafrom the sensing devices. The processor may determine the position ofperforation guns using the data from the sensing devices. Programmableevents, which may include detecting a radioactive tag or detecting acollar, may trigger position determination. The sensing devices mayinclude an accelerometer, pressure sensor, and gyroscope.

While the present disclosure has been described with respect to alimited number of embodiments, those skilled in the art will appreciatenumerous modifications and variations therefrom. It is intended that theappended claims cover all such modifications and variations.

1. A method of performing real-time run-in position sensing comprising:conveying a tool attached to a tubular string in a borehole, wherein thetool comprises a position sensing sub, and wherein the position sensingsub comprises multiple sensing devices; recording measurements taken bythe sensing devices; combining the measurements to determine a positionalong the borehole of a particular portion of the tubular string,wherein data from sensing devices having a higher priority overridesconflicting data from sensing devices having a lower priority; andtransmitting the position wirelessly.
 2. The method of claim 1, whereinthe sensing device with the highest priority comprises a radiationsensor that detects a radioactive tag.
 3. The method of claim 1, whereinthe sensing devices comprise an accelerometer and a gyroscope.
 4. Themethod of claim 1, wherein the sensing devices comprise a rollercounter.
 5. The method of claim 4, wherein the roller counter compriseswheels that turn as the tool is conveyed in the borehole, and whereinrecording the measurements comprises determining the accuracy of thewheels.
 6. The method of claim 5, wherein determining the accuracycomprises determining the wheel that has turned the maximum number oftimes over a programmable distance along the borehole and recording thatnumber as a measurement for use in position determination.
 7. The methodof claim 6, comprising repeating the determining and recording overanother programmable distance along the borehole.
 8. The method of claim1, wherein the tubular string comprises perforation guns, and whereindetermining the position comprises determining the position of theperforation guns.
 9. The method of claim 8, further comprisingactivating the perforation guns after determining the position withoutbringing the tool out of the borehole.
 10. The method of claim 8,wherein the tool is attached to the tubular string at a known distancefrom the perforation guns.
 11. The method of claim 1, whereindetermining the position comprises determining the position of theposition sensing sub.
 12. The method of claim 1, further comprisingassembling the tubular string such that the position sensing sub residesbelow a packer and above perforation guns when within the borehole. 13.The method of claim 1, wherein programmable events trigger positiondetermination and updating of an error factor used to calibrate theposition.
 14. The method of claim 1, wherein determining the positioncomprises determining the position repeatedly over programmabledistances along the borehole.
 15. An apparatus for performing real-timerun-in position sensing comprising: a hierarchy of sensing devices,wherein the sensing devices measure conditions within a borehole as theapparatus is conveyed along the borehole while attached to a tubularstring; a processor coupled to the sensing devices, wherein theprocessor determines position using data from the sensing devices, andwherein data from sensing devices having a higher priority overridesconflicting data from sensing devices having a lower priority duringposition determination; and telemetry equipment coupled to theprocessor, wherein the telemetry equipment wirelessly communicates theposition.
 16. The apparatus of claim 15, wherein the sensing devicesfurther comprise a radiation sensor for detecting a radioactive tag, aroller counter, and a collar locator for detecting collars, and whereinthe radiation sensor has the highest priority.
 17. The apparatus ofclaim 15, wherein the processor determines the position of the apparatususing the data from the sensing devices.
 18. The apparatus of claim 15,wherein the processor determines the position of perforation guns usingthe data from the sensing devices.
 19. The apparatus of claim 15,wherein programmable events, comprising detecting a radioactive tag ordetecting a collar, trigger position determination.
 20. The apparatus ofclaim 15, wherein the sensing devices comprise an accelerometer,pressure sensor, and gyroscope.